Method for inspection of metal tubular goods

ABSTRACT

A method for predicting the performance of tubular goods includes using a computer readable three-dimensional representation of tubular good which includes computer readable measurements of discrete segments of the wall of said tubular acquired by ultrasonic detection means, along with associated data representing the position of discrete segment and optionally ovality data to predict the effect of stress conditions, including tensile, bending, collapse, burst and aging forces upon said tubular and optionally analyzing sequential inspection of the same tubular good over a period of time predict when failure is likely to occur, and to avoid failure while maximizing the use of the tubular good.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuing patent application emanating frompresently pending U.S. patent application Ser. No. 12/137,341 filed Jun.11, 2008, which is a continuing patent application emanating from U.S.patent application Ser. No. 11/849,287 filed Sep. 1, 2007 (now U.S. Pat.No. 7,401,518 issued Jul. 22, 2008), which is a continuing patentapplication emanating from U.S. patent application Ser. No. 10/548,731filed Sep. 7, 2005 (now U.S. Pat. No. 7,263,887, issued Sep. 4, 2007),which emanated from International Patent Application NumberPCT/US04/07010 filed Mar. 8, 2004 which claims priority to theProvisional Patent Application No. 60/452,907 filed Mar. 7, 2003.

FIELD OF THE INVENTION

The invention disclosed herein relates to non-destructive inspection oftubular metal goods. More particularly the invention herein disclosedrelates to a non-destructive means for determination of wall conditions,in particular wall thickness data, of tubular metal goods by use ofultrasonic detection apparatus. With additional specificity theinvention disclosed herein relates to an improved method of collecting,storing, displaying and otherwise utilizing information resulting fromultrasonic detection of the wall of metal tubulars. With even morespecificity the invention herein disclosed relates to the use ofultrasonic means to acquire incremental data representing small,discrete sections of a tubular wall in association withthree-dimensional positional data pertaining to each small, discretesection, so that the wall of a metal tubular (or portions thereof) canbe displayed, imaged, examined and utilized in simulative/comparativeprograms as a three-dimensional object.

BACKGROUND OF THE INVENTION

In many applications inspection of metal tubular goods for the presenceof possible defects is highly desirable and/or required. Inspection ofmetal tubulars is common in, for instance, the oil and gas explorationand production industry, in refineries and/or in chemical and otherplants, where the failure of such tubulars may result in seriousconsequences.

The art of inspecting metal tubulars for possible defects hasexperienced various improvements over the course of time. Early testingwas rudimentary. It sometimes consisted of no more than visualinspection of the exterior of the tubular for such defects as might beseen. This method was obviously limited. Sometimes inspection mightinclude an attempt to “ring” or “sound” the tubular. This generallyinvolved striking the tubular with a hard object, such as a hammer, andlistening to the sound the tubular produced. An abnormally “flat” tonemay indicate that the tubular was cracked. This method was highlysubjective and even if employed by skilled personnel was unable todetect small defects.

The need to improve inspection of metal tubulars led to otherdevelopments, such as magnetic testing. One method of magnetic testinginvolved magnetizing the tubular (or a portion thereof), “dusting” samewith ferromagnetic powder and then visually inspecting for abnormaldistribution of the powder. In another method of magnetic testing anelectromagnetic coil was passed close to the surface of the tubular andvarious means used to determine disturbance of the induced eddy currentpossibly being caused by discontinuities in the tubular. Neither methodwas well suited for detection of small defects and/or those below thesurface of the tubular, were time consuming, were largely dependent onthe skill of the operator and did not produce precise data from whichthe effect of a condition found might be mathematically calculated.

Another attempt to improve inspection of metal tubulars was the dyepenetrant method. In such method the tubular was cleaned, coated with apenetrating fluid containing dye (typically of a type which wouldfluoresce under certain lighting conditions), wiped and then visuallyinspected for surface discontinuities still containing dye. This methodwas not useful for detection of sub-surface defects and did not produceprecise data from which the effect of a condition found might bemathematically calculated.

Another means to inspect metal tubulars is by utilization of X-rays.While x-ray represents a way to determine some defects below the surfaceof the tubular wall, certain defects such as thin cracks anddelaminations are difficult to find by X-ray. Moreover this method ofinspection does not produce precise data from which the effect of acondition found might be mathematically calculated. Because of thedanger, shielding requirements, expense and limitations of thistechnology, its use has been limited.

An attempt to inspect metal tubular goods for wall thickness defects wasrepresented by utilization of gamma radiation. In one method the gammasource is placed on one side of the tubular and a radiation sensor onthe other side of the tubular. By measuring the decrease in radiation asit passes through the tubular an estimation of the collective wallthickness of both sides of the tubular can be made. This method hascertain disadvantages, including but not necessarily limited to relativeinsensitivity of the sensor to small thickness changes, its inability todetect if one side of the tubular is thick and the other thin (which isnot an uncommon defect, particularly in extruded tubulars) and thesafety, security and administrative issues relating to utilization ofradioactive sources. Moreover such inspection does not produce data fromwhich the effect of a condition found might be calculated withmathematical precision.

In attempt to avoid the limitations of the above technology, ultrasonictechnology was developed for inspection of tubular goods. In general,this technology is based on the speed of sound in metal and the factthat a sound wave will reflect (“echo”) from medium interfaces. Thus bypropagating a sonic wave in said metal and by measuring the time ittakes for echos of that wave to return from an interface, it is possibleto determine the precise distance to said interface. Such interface may,of course, be the opposite wall of the tubular. Accordingly by use ofultrasonic means precise wall thickness of a tubular at an area may bedetermined. In order to determine the wall thickness of a tubular aboutthe whole area of the tubular, the tubular is typically rotated aboutits axis and advanced longitudinally in relation to an ultrasonic headwhich periodically “fires” and effectively samples wall thickness underthe head at the time. As the tubular advances a stream of data points,each one representing a wall thickness measurement is generated.Typically the data resulting from such testing is displayed intwo-dimensional form, as a numeric table or as a line on a graph(representing wall thickness at a position on the length of thetubular). Out-of-range values can be detected either by human readingthe table or graph, or by machine (computer) detection of out of rangevalues. From such data the general location of a suspected defect alongthe length of tubular, its magnitude and direction (whether too thin ortoo thick) can be determined and the tubular joint marked foracceptance, rejection or repair, but said data was not useful forsubstantial purposes therebeyond. Namely, without three-dimensional dataas to both the defect and the remainder of the tubular, the effect thatdefect might have concerning performance of the tubular could not becalculated with mathematical precision.

The invention disclosed herein relates to improved method to acquire,collect, assemble, store, display and/or utilize data stemming fromultrasonic inspection of tubular goods, not only for a determination forthe presence or absence of defects, but so that data from the inspectionmay be used to calculate projected performance of the tubular with amathematical precision not previously available by non-destructiveevaluation of the tubular.

OBJECTS OF THE INVENTION

The general object of the invention disclosed herein is to provide animproved means for collection, assembly, storage, display, analyze andother utilization of information derived from ultrasonic inspection oftubular goods. A particular object of the invention is associate datarepresenting incremental ultrasonic measurements of wall of discrete,small sections of a tubular with three-dimensional positionalinformation identifying each discrete section of the tubular at whicheach wall measurement was obtained, so that the data may be displayed,presented, analyzed and otherwise used (either by visual means ormathematically) as a three-dimensional object. Another object of theinvention is to collect, assemble and/or store wall thickness data ofmetal tubulars in a form which is susceptible to display, presentation,analysis or other use as a three-dimensional object, including but notlimited to display, presentation and analysis as a three-dimensionalimage which my be viewed from any perspective, zoomed, rotated, eachdata point individually examined, used in mathematical calculationspredicting performance of the tubular under certain conditions, comparedwith previous or subsequent data and thereby used to project futurechanges, used in engineering calculations and/or programs which predictresponse of the tubular to various stressors and otherwise haveincreased utility.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

While the present invention will be described with reference topreferred embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, modifications may be made to adapt a particular situation ormaterial to the teachings of the invention without departing from theessential scope thereof. It is therefore intended that the presentinvention not be limited to the particular embodiments disclosed herein,but that the invention will include all embodiments (and legalequivalents thereof) falling within the scope of the appended claims.

In order to practice the invention herein disclosed an ultrasonic meansis provided for measuring the wall of small areas of a metal tubular. Inpreference this will be accomplished by positioning an ultrasonic headin close proximity to the exterior of the tubular and substantiallyperpendicular to both the longitude and a tangent of the tubular. Inpreference said head will include an ultrasonic transducer forpropagating an ultrasonic wave radially inward (towards the longitudinalaxis of the tubular) and for receiving ultrasonic reflections (“echos”)returning from the opposite direction. In preference said head will becoupled to the tubular by a medium which effectively transmitsultrasonic waves across the interface between the medium and thetubular, for example by water coupling, or by other means well known inthe field of art.

As is well known, by accurately measuring the length of time it takesfor the ultrasonic wave to travel from the outer wall of the tubular tothe interior wall, reflect from the interior wall and return to theouter wall (known as “time-of-flight” or “TOF”), the distance (“D”) thewave has traveled may be readily calculated [from the formula D(distance)=S(speed)×TOF, the speed of sound in various metals being wellknown]. Wall thickness of the tubular at the area so sampled is one-halfof “D”.

While those skilled in the art will realize that there are many otherpractical considerations to obtaining accurate measurement of the wallthickness of a tubular at a particular location by ultrasonic means,including but not limited to, issues relating to ultrasonically couplingthe transducer and tubular, issues relating to excluding the effects ofcoupling from the calculations, issues relating to excluding subsequentreflections from the surfaces, issues relating to accurately “starting”and “stopping” timing measurements in a precise and consistent manner,and, other such issues. As these considerations, and various solutions,are well known to those skilled in the art, they will not be furtherdiscussed herein. As it relates to the invention disclosed, it is onlynecessary that some ultrasonic means be provided to obtain incrementalmeasurements of small, discrete selectable sections of the tubular byultrasonic means.

In order to practice the invention, a means must also be provided toobtain incremental measurements of small, discrete wall segmentsthroughout the entire area of the tubular of interest (which in mostcases will be the entirety of the tubular). In the preferred embodimentthis is accomplished by rotating the tubular about its longitudinal axisas the ultrasonic head advances longitudinally along the length of thetubular, and periodically triggering (“firing”) the ultrasonic head tomake a wall measurement (a “snapshot”) of the area of the tubularadjacent thereto at the time. In preference the rate of rotation,longitudinal advance, rate of triggering the ultrasonic head, and sizeof the ultrasonic head will be such that each snapshot of the wallpartially overlaps, both circumferentially and longitudinally withadjacent snapshots, so that complete coverage of the entire area of thetubular to be inspected (which will in most cases be the entire tubular)is obtained. In the preferred embodiment of the invention this isaccomplished by disposing the tubular horizontally on a roller systemwhere it may be rotated about its longitudinal axis. In preference theultrasonic head will be above and adjacent to the upper surface of thehorizontally tubular and pointed so as to propagate wavesperpendicularly downward toward the tubular. In preference the tubularwill be rotated at constant speed, and as it is so rotated, theultrasonic head advances longitudinally at constant speed, so that therelative movement between the head and the tubular substantially followsa spiral path along the outer surface of the tubular. As the tubular isso advanced the ultrasonic head is periodically fired to take a snapshotof the wall of the tubular. Each of these snapshots is a mathematicalrepresentation, a “number”, which represents wall thickness of thetubular under the ultrasonic head at the time it is fired. Each of thesesnapshots will be recorded. Accordingly, at the end of the process aplurality of incremental wall thickness snapshots will have beenrecorded which represents at least partially overlapping coverage of theentire area of the tubular to be inspected (which will in most cases bethe entirety of the tubular).

It will be appreciated by those skilled in the art that a similar resultmight be obtained by “sampling” (incrementally obtaining datarepresenting small, discrete sections of the wall of a tubular) in adifferent manner or order. It will be appreciated that the tubular couldbe disposed other than horizontally during sampling or even disposed invarying positions during sampling. It will be appreciated that samplingmight be done by incremental rotation and/or longitudinal advancementand stopping of the tubular, rather than continuous rotation andlongitudinal advancement of the tubular (or ultrasonic head) duringsampling. It will be appreciated that sampling might be accomplishedalong a plurality of longitudinal lines about different circumferencesof the tubular, or by a plurality of circular lines about differentlongitudes of the tubular, rather than by sampling along a spiral path.It will be appreciated that the ultrasonic head may be rotated about thetubular rather than the reverse. It will be appreciated that the tubularmay be advanced longitudinally with respect to the ultrasonic headrather than the reverse. It will be appreciated that multiple ultrasonicheads may be used. It will be appreciated that sampling may even beaccomplished in a random manner. All of these permutations are intendedto be comprehended by the invention disclosed herein, the thrust ofwhich does not relate to the particular order in which discretesnapshots of small wall segments of the tubular are obtained andrecorded for the entirety of the area of the tubular to be inspected,but that such result is obtained. Namely at the end of the sampling itis desired to have obtained and recorded, with mathematical precision, aplurality of snapshots of the wall of the tubular, each of whichrepresents a wall thickness of a small discrete section of the tubular,in combination with all of the snapshots covering the entire area of thetubular of interest.

In addition to recording discrete snapshots of small sections of thetubular wall over the entire area of the tubular of which is of interest(which in most cases will be the entire tubular), in the inventiondisclosed herein positional information will also be obtained andrecorded as to the location on the surface of the pipe at which eachsnapshot was taken. In addition thereto, each particular snapshot willbe associated with the particular positional information unique to thatsnapshot.

In the preferred embodiment of the invention, the position of eachsnapshot of the wall of the tubular is obtained by marking the exteriorof the tubular with a longitudinal line which is detectable byphotoelectric cell. This line forms a circumferential reference which inthe preferred embodiment is treated as a “zero degree” reference. Thoseskilled in the art will know the reference need not necessarily beconsidered a zero degree reference, but could in fact be given any othermathematical value (all of which are comprehended by the invention).Each time the tubular is rotated the photoelectric cell is triggered bythe reference line. In the preferred embodiment of the invention, eachtime the cell is triggered the stream of data (representing a stream ofdiscrete wall thickness measurements) is “marked” with an indicationthat one rotation of the tubular has occurred. In the preferredembodiment of the invention within each rotation each is assigned anumerical value representing the order within that rotation which thatparticular snapshot was taken (i.e., the first snapshot followingtriggering of the photoelectric cell will be assigned a valuerepresenting 1, the second snapshot assigned a value representing 2,etc.). Those skilled in the art will recognize that any mathematicalvalue could be assigned so long as the assigned value could besubsequently correlated to a circumferential position at which eachsnapshot could be taken, therefore is comprehended by the inventiondisclosed herein.

Within each rotation of the pipe the numerical value representing theorder in which each snapshot within that revolution of the pipe may ofcourse be converted to a value which represents the angle, from thereference line, at which that snapshot was taken or, in conjunction withknowing the position along the longitude of the tubular at which thatrotation occurred, may be converted to some other form (for example,traditional “X, Y, Z” coordinates) which represents the position on thetubular at which each snapshot was taken.

In the preferred embodiment of the invention the data representing onerotation of the pipe is longitudinally synchronized with snapshots ofanother revolution of the tubular, so that accurate alignment of dataalong a longitude is maintained, even if speed of rotation of thetubular was not exactly the same in one rotation as another rotation, orother conditions have occurred where the number of snapshots in onerevolution of the tubular is not exactly the same as the number ofsnapshots in other revolutions. In the preferred embodiment of theinvention, synchronizing the circumferential data once each revolutionof the tubular has been found adequate. In the preferred embodiment ofthe invention, synchronization is accomplished by computer means whichconverts the value which represents the order in a particular revolutionpertaining to each snapshot to a value which represents angular positionof each snapshot about the circumference of the tubular. Thus, if in onerevolution there were 400 data points (each of which represented a wallthickness reading, or “snapshot”), the 100th data point will beconverted to a value which will interpreted to be 90° from the referencemarking, the 200th data point converted to a value representing 180°from the reference marking, etc. Whereas if in a different revolutionthere are 500 data points, then the 125th data point will be convertedto a value which will be interpreted to be 90° from the referencemarking, the 250th data point converted to a value representing 180°from the reference marking, etc. In this way all the data points in onerotation of the tubular are longitudinally synchronized with all datapoints corresponding longitudinally in other revolutions of the tubular.It will be appreciated that synchronization of data could beaccomplished more frequently or less frequently than once eachrevolution, or by means other than use of an external reference linedetectable by a photoelectric cell. It will be appreciated that insteadof converting position of the discrete snapshots about the circumferenceof the tubular into angular format, said position could be representedas a point in any coordinate system. For purposes of the inventiondisclosed herein it does not matter how the position about thecircumference of the tubular that each of the discrete snapshots of thewall thickness is mathematically represented, but rather that suchcircumferential information about each snapshot is obtained and recordedwith mathematical precision.

In the preferred embodiment of the invention not only willcircumferential position of each wall thickness measurement (“snapshot”)be obtained, but longitudinal position of each snapshot will also beobtained, recorded and associated, with mathematical precision, to eachdiscrete snapshot. In the preferred embodiment of the invention it isthe ultrasonic head which moves along a line parallel to the axis of thetubular during inspection thereof. In the preferred embodiment of theinvention a sensor on said head generates a signal as to its positionalong the longitude of the tubular each time the transducer is fired.Thus in the preferred embodiment this signal is recorded each time thehead is fired (to take a wall thickness reading, a “snapshot” of thewall). Those skilled in the art will recognize that longitudinalposition of each snapshot might be obtained by other means, includingbut not limited to measuring the relative speed of longitudinal movementbetween the tubular and ultrasonic head as a function of time, countingthe number of revolutions it takes for a tubular to advance a certaindistance in respect to the head and thereby calculating the point alongthe spiral path which each snapshot was taken, or other means. Forpurposes of the invention disclosed herein the particular manner ofobtaining the longitudinal position at which each wall thicknesssnapshot is taken is not important, but rather that such data isobtained, recorded and associated with each snapshot, with mathematicalprecision. Accordingly at the conclusion of the process there will havebeen obtained and recorded a plurality of overlapping measurements ofsmall discrete sections of the wall of the tubular. Each measurementwill include a mathematically precise representation of wall thicknessand be associated with a mathematically precise three-dimensionalrepresentation the place on the tubular where that measurement of thewall was obtained from. The plurality of such readings will cover theentire area of the wall of interest, which in most case may be theentire tubular.

It will however be appreciated that the invention is not so limited.Namely the entire area of the tubular need not necessarily be sampled.Rather by appropriately triggering the ultrasonic head to fire onlybetween certain areas of the rotation of the tubular one might limitinspection to the longitudinal weld line of the pipe. Alternatively theultrasonic head may be adjusted to fire only at certain longitudinalpositions of the pipe, thus, for instance limit inspection to certainareas along the length of the pipe. Alternatively both might be theultrasonic head may be set to only within certain circumferential orlongitudinal limits, defining a relatively small section of the pipe tobe inspected according to the invention. Such permutations are fullycomprehended by the invention.

It will also be appreciated that sampling according to the inventionneed not necessarily be of contiguous areas of the pipe, or compriseoverlapping snapshots. It is comprehended that the invention may beutilized with spaces between snapshots. While leaving spaces betweensnapshots may fail to reveal a small defect in the space not sampled,the data gathered by the invention will still form that of a virtualthree-dimensional object which has utility, for instance in simulativeand modeling programs, far above that currently available.

So far as synchronization of longitudinal data, such synchronization hasnot been found necessary if the tubular is rotated according to thepreferred embodiment discussed above, because while there are aplurality of rotations of the tubular (which may require synchronizationas discussed above), there is only one longitudinal advancement of thetubular. Accordingly there is no plurality of discrete sets of data,each representing a discrete longitude of the tubular, to besynchronized with other data also representing a longitude of thetubular. This would be different if the data were gathered or recordedin a different manner which resulted in different sets of data, each ofwhich said sets represented a longitude of the tubular. In thisinstance, it would be desirable to convert the number of data points ineach set to correspond to the known length of the tubular, so that thediscrete sets of longitudinal data would correspond to that length andtherefore each other. Accordingly, comprehended by the invention hereinis circumferential and/or longitudinal synchronization of data, as maybe necessary.

In the preferred embodiment of the invention, effective size of thetransducer is about one-half inch in diameter. Accordingly, in thepreferred embodiment of the invention, to assure full coverage of thearea of interest in the preferred embodiment described above, a rate ofrotation and triggering of the transducer is selected so that thetransducer each triggered as the tubular rotates about ⅜th inch (orless), and each rotation of the tubular results in a longitudinaladvancement of the tubular about ⅜th inch (or less). It will beappreciated by those skilled in the art that rate of rotation andadvancement would vary if a transducer of different size were used, theobjective being to assure snapshots which partially overlap. It will beappreciated that the smaller the effective area of the ultrasonic headthe finer resolution of wall thickness will be obtained, but at thesacrifice of speed and accumulation of larger amounts of data.

It may be appreciated that since in the preferred embodiment of theinvention each snapshot (representing measurement of wall thickness ofthe tubular at a discrete location) at least partially overlaps adjacentsnapshots, at least where such overlap occurs there may be two, possiblymore, measurements of wall thickness. It may be also appreciated thatthe measurements may not be exactly the same, since each covers at leasta portion of the surface that the adjacent snapshot does not cover. Itmay be appreciated that where such overlap occurs and is not identical,there is presented an ambiguity as to the value to be assigned the wallthickness where such overlap occurs. In the preferred embodiment of theinvention it is the value which represents the smallest (“thinnest”)wall thickness which is assigned this area, because a thin wallcondition is believed to represent the greatest risk of failure of thetubular. However, this does not have to be so. The value whichrepresents the thickest wall section could as easily be used, or anaverage between the multiple reading could be assigned to the area wheresuch overlap occurs. All are comprehended by the invention hereindisclosed.

Accordingly, in the preferred embodiment of the invention, partiallyoverlapping wall thickness measurements representing discrete,incremental, overlapping measurements of small areas of the tubular aswell as positional information of each discrete measurement of wallthickness will be obtained and will be associated with each other. Inthe preferred embodiment of the invention the requisite association ofeach discrete measurement of wall thickness with the positionalinformation pertaining to that measurement is accomplished by digitalmeans. That is both measurement of wall thickness and positionalinformation are converted to digital format appended together as onedata point. Those skilled in the art will recognize that other forms ofassociation, including but by not limited to use of cross-referencetable, would also work. For purpose of the invention the manner thateach discrete measurement of wall thickness is associated withrespective positional information is not of particular importance, onlythat such association be made. It is however particularly useful (whilethe invention is not limited thereby) that such data be associated in aform that is readable by computer means, in order to facilitate computerdisplay, analysis and use of the information.

Data contained in such format may be used in ways not previouslypossible. For instance, the data representing wall thickness may be, bycomputer means, shade and/or color coded and presented in virtualthree-dimensional form, which clearly resembles visual inspection of thetubular, or sections of particular interest, from almost anyperspective, from any apparent distance, with or without enlargement, asif the walls of the tubular were color and/or shaded coded (differentthicknesses represented different colors and/or shades).

Moreover, the precise numerical value of the thickness of any sectionand its precise location on the tubular, may be obtained from suchpresentation. While the preferred embodiment of the invention uses “OpenGL” computer graphic rendering software to display the tubular data,those skilled in the art will recognize that other computer graphicrendering software could be used as well.

Moreover the data contained in digital format which represents wallthickness of each incremental section of a tubular and the location ofthat section can be used in computations which predict the actual effecton the tubular to various stressors, including tensile, bending,collapse and burst forces, aging, etc. Particularly useful by sequentialinspection of a tubular, is the ability to analyze changes which haveoccurred over a period of time, and thereby be able to accuratelypredict, prior to failure of the tubular, when failure is likely tooccur, thereby avoid same, but at the same time maximize use of thetubular.

In addition to the discussion above, the data can be associated withother measurements of the tubular which may be of interest. For instanceother means, such as cam following means, ultrasonic means, laser means,and other means for collecting pertaining to ovality of the tubular canalso be associated with wall thickness data, positional information orboth. Likewise, not only may wall thickness and ovality data beassociated with positional information, but data derived from othermeans (typically ultrasonic means generating “sheer waves”) designed todetect defects within the wall of the tubular, such as inclusions,voids, delaminations, etc. may also be associated with positional data.By so doing this other information would thereby become subject todisplay, presentation, analysis or other use as three-dimensional data.

It is thus to be appreciated that a process established in accordancewith the principles and teachings of the present inventive disclosureconstitutes an advancement in the field of art to which the inventionpertains. While the above description contains many specificities, theseshould not be construed as limitations on the scope of the invention,but rather as an exemplification of preferred embodiments thereof.Accordingly, the scope of the present invention should be determined notby the embodiments illustrated, but by such claims as may be allowed andtheir legal equivalents.

1. Method for predicting performance of tubular goods, comprising: a.positioning an ultrasonic detection means which is capable of measuringthe thickness of a discrete section of the wall of a tubular good in aplurality of adjacent, partially overlapping sampling positions spacedlongitudinally and circumferentially along an area to be inspected ofthe wall of a tubular good; b. at each sampling position, causing saidultrasonic detection means to determine the thickness of a discreteportion of the wall of said tubular good; c. for each sampling position,determining the longitudinal position of said ultrasonic detection meansalong the axis of said tubular good and the circumferential position ofsaid ultrasonic detection means about the circumference of said tubulargood; d. recording the measurements of wall thickness in an associatedrelationship with their corresponding longitudinal positions andcircumferential positions to form a computer-readable, three dimensionalrepresentation of the wall of the tubular good over the area to beinspected; and e. using the three-dimensional representation incomputations to predict the effect of specific stress conditions on thetubular good.
 2. The method of claim 1 wherein said stress conditionscomprise at least one of tensile, bending, collapse, aging and burstforces.
 3. The method of claim 2 wherein said computations furthercomprise data as to ovality of the tubular good.
 4. The method of claim3 wherein said area of interest comprises the entire wall of the tubulargood.
 5. The method of claim 4 wherein said step (a) comprises advancingthe ultrasonic detection means and the wall of the tubular goodlongitudinally relative to one another while rotating the tubular goodabout its longitudinal axis.
 6. The method of claim 5 wherein in step(b) the ultrasonic detection means is triggered periodically to generatea stream of discrete wall thickness measurements following asubstantially helical path on the wall of the tubular good, whiledetecting and marking in the stream of measurements each completerotation of the tubular good.
 7. The method of claim 6 whereindetermining the circumferential position in step (c) comprisesconverting the position of a measurement in the stream to arepresentation of its circumferential position by reference to thenumber of measurements made in a complete rotation containing thatmeasurement.
 8. The method of claim 7 further comprising repeating thesteps (a) to (f) for sequential inspection of the same tubular good andanalyzing changes which have occurred over a period of time to predictwhen failure is likely to occur, and to avoid failure while maximizinguse of the tubular good.
 9. The method of claim 8 applied to theinspection of tubular goods for use in oil and gas exploration orproduction.
 10. The method of claim 2 wherein said area of interestcomprises the entire wall of the tubular good.
 11. The method of claim10 wherein said step (a) comprises advancing the ultrasonic detectionmeans and the wall of the tubular good longitudinally relative to oneanother while rotating the tubular good about its longitudinal axis. 12.The method of claim 11 wherein in step (b) the ultrasonic detectionmeans is triggered periodically to generate a stream of discrete wallthickness measurements following a substantially helical path on thewall of the tubular good, while detecting and marking in the stream ofmeasurements each complete rotation of the tubular good.
 13. The methodof claim 12 wherein determining the circumferential position in step (c)comprises converting the position of a measurement in the stream to arepresentation of its circumferential position by reference to thenumber of measurements made in a complete rotation containing thatmeasurement.
 14. The method of claim 13 further comprising repeating thesteps (a) to (f) for sequential inspection of the same tubular good andanalyzing changes which have occurred over a period of time to predictwhen failure is likely to occur, and to avoid failure while maximizinguse of the tubular good.
 15. The method of claim 14 applied to theinspection of tubular goods for use in oil and gas exploration orproduction.
 16. The method of claim 1 wherein said area of interestcomprises the entire wall of the tubular good.
 17. The method of claim16 wherein said step (a) comprises advancing the ultrasonic detectionmeans and the wall of the tubular good longitudinally relative to oneanother while rotating the tubular good about its longitudinal axis. 18.The method of claim 17 wherein in step (b) the ultrasonic detectionmeans is triggered periodically to generate a stream of discrete wallthickness measurements following a substantially helical path on thewall of the tubular good, while detecting and marking in the stream ofmeasurements each complete rotation of the tubular good.
 19. The methodof claim 18 wherein determining the circumferential position in step (c)comprises converting the position of a measurement in the stream to arepresentation of its circumferential position by reference to thenumber of measurements made in a complete rotation containing thatmeasurement.
 20. The method of claim 19 further comprising repeating thesteps (a) to (f) for sequential inspection of the same tubular good andanalyzing changes which have occurred over a period of time to predictwhen failure is likely to occur, and to avoid failure while maximizinguse of the tubular good.
 21. The method of claim 20 applied to theinspection of tubular goods for use in oil and gas exploration orproduction.